OBJECTIVES: Integumental reactivity: to evaluate the effect of aging on a variety of skin responses to specific excitants in order to construct a kinetic "profile" on skin behavior. Semi-quantitative data will be obtained on such basic functions as wound-healing, inflammatory responses and vascular reactivity. Cell mediated immunity: to evaluate the effect of aging on the capacity to develop sensitization to dinitrochlorobenzene. Stratum corneum biology: to assess quantitatively the changes in organization and dynamics of the horny layer in relation to aging. Photobiology: to characterize the responses of human skin to ultraviolet light (UV) in relation to aging. Eccrine sweating: to assess sweat gland function in relation to age. Sebaceous gland physiology: to determine quantitative and qualitative changes in sebaceous secretion in relationship to aging. Microbiology: to determine quantitatively the resident microflora in relation to age.